The present application relates to anchors for attaching an elongated member to a bone, and more particularly to anchors with a two member securing mechanism to prevent the elongated member from escaping from the anchor.
Elongated members such as but not limited to rods, wires, and tethers, are used in a variety of different surgical applications. The elongated members are attached to a bone in a patient and may provide a corrective force, support, or positioning for the bone and other adjacent bones. The elongated members are attached to the bone by anchors that include a receiver and a shaft. The receiver is configured to receive the elongated member, and the shaft is configured to attach to the bone. Many previous anchors include a set screw that is threaded onto the receiver to capture the elongated member. The threaded set screw design may include several drawbacks.
One drawback of a threaded set screw design is the set screw may be threaded improperly onto the receiver. This may cause the threads to be stripped on the receiver and/or set screw. The set screw may bind within the receiver preventing further tightening of the set screw to fully engage the elongated member. Alternatively, the set screw is thereafter removed from the receiver but the threads on the receiver are stripped requiring removal and replacement. Another issue may be the false impression that the set screw is fully tightened in the receiver and engaged with the elongated member. At some point thereafter, the improperly threaded set screw loosens in the receiver requiring a revision procedure.
Another drawback is the set screw may cause the arms of the receiver to splay apart. The set screw may apply an outward force on the arms of the receiver as it is threaded onto the receiver. This force may cause the arms to move apart which may cause the set screw to become loosely attached to the receiver. Again, this may result in the set screw not fully engaging the elongated member, and/or the set screw becoming loose which would require correction during a revision procedure.